95 civic vx w/gsr ...putting foot to floor and rpm

i have a 95 civic vx with a gsr swap ... its been funny fine for months now and the other day it started acting up . its done this a few times now but runs fine most of the time . the car will act like its going to stall but it dont stall . I can put my foot to the floor and the rpms will not go up past 2000 rpms . i changed the plug and wires and oil and it still is doing it every now and then . . also there is no o2sensor on the car but its always been like that and ran fine for the last 4 months . If you have any clue please let me know thanks